1. Field of the Invention
The present invention is directed to an x-ray image intensifier of the type used in an x-ray imaging system, such as for medical diagnostics.
2. Description of the Prior Art
X-ray image intensifiers are used in x-ray diagnostics systems to convert an x-ray shadow image, produced by transillumination of a patient with x-rays, into a visible image. A video camera tube is connected to the output screen of the x-ray image intensifier, and supplies signals corresponding to the output of the x-ray image intensifier to a video monitor, via a video chain. The examination area is displayed on the monitor as a viewable image.
An x-ray image intensifier is disclosed in U.S. Pat. No. 3,688,146 having a tubular evacuated vessel with an input luminescent screen with a photo-cathode situated at one end face thereof, and having an electrode system, for accelerating and focusing the electrons which are generated upon incidence of x-radiation on the input luminescent screen, onto an output luminescent screen, arranged at the other end face. The electrode system has a plurality of cylindrical or annular electrodes of different diameters, to which respectively different voltages are applied for focusing the electrons generated at a point of the input luminescent screen onto a corresponding point of the output luminescent screen. These electrodes are applied to the inside of the tubular wall of the x-ray image intensifier as a metal coat over areas having different diameters. The tubular wall consists of insulting material. A conductor is fed through the tubular wall for voltage supply to the electrodes, and is in electrical contact with the metallic coat.